We report a controllable delay of the probe light pulse sequence by a master, saturating pulses of significantly different wavelength (at 1526 and 1568 nm respectively) observed in erbium-doped single-mode fiber with saturable absorption.
We report controllable (slow or fast) propagation of low-intensity probe-light pulses through erbium-doped fiber periodically saturated by the synchronized master-pulse sequence. These two pulse sequences could have significantly different carrier wavelengths within the fundamental absorption spectrum 1470-1570 nm of Er(+3) ions. The effect of fractional delay or advancement grew with the fiber optical absorption at the probe wavelength and could be significantly stronger than that at the saturating wavelength. The probe-pulse advancement was observed in the case when the saturating and probe waves were modulated approximately in antiphase. The observed effects are explained in the framework of a simple model of a periodically saturated homogeneously broadened absorption line.
We report experimental observation of slow or fast light in configuration of counterpropagating saturating and probe waves in erbium-doped fibers with saturable absorption. The delayed or accelerated probe light propagation is shown to be associated with two-wave mixing (TWM) between these two waves via dynamic population grating. As compared with recording at 1526 nm from the central region of Er3+ fundamental absorption spectrum, at 1485 nm, the population grating has significant admixture of the refractive index component. This results in a significant asymmetry of the TWM-induced transmittance of the probe wave as a function of the frequency offset $\ensuremath{\Delta}\ensuremath{\Omega}$ between the waves and shifts position of the maximum group delay from zero $\ensuremath{\Delta}\ensuremath{\Omega}$. The same reason ensures appearance of a significant group advancement for the frequency offset of the opposite sign.
We report experimental results on the 1550 nm modulated light propagation in a closed-loop all-fiber resonance configuration, which includes a segment of the erbium-doped fiber with saturable optical absorption. It is shown that by a simple increase of the average incident light power, one can switch from the undercoupling to the overcoupling with the closed-loop cavity, which leads to a dramatic change from advancement to delay in the transmitted optical signal with the resonance carrier frequency. In the reported experiments with the ≈4.4 m long closed-loop cavity (with a 2.4 m long EDF segment) we observed a switch from ≈0.26 fractional advancement to ≈0.65 fractional delay in 166 ns periodic light pulses with a resonance frequency in the 1550 nm wavelength range when the average incident power was changed from 0.09 to 0.6 mW.
We observe both extremely slow and superluminal pulse propagation speeds at room temperature in an erbium-doped fiber (EDF). A signal at 1550 nm is sent through an erbium-doped fiber with varying powers of a 980 nm pump. The degree of signal delay or advancement is found to depend significantly on the pump intensity. We observe a maximum fractional advancement of 0.124 and a maximum fractional delay of 0.089. The effect is demonstrated both for a sinusoidally modulated signal and for Gaussian pulses. The ability to control the sign and magnitude of the pulse velocity could have important implications for applications in photonics.
Erbium-doper fiber (EDF) is a flexible and promising model medium for investigation of the slow/fast light propagation in saturable optical materials. The experiments are usually performed in the spectral range 1480-1570 nm of the absorption/gain of Er3+ ions using the input power of a sub-mW scale. Conventional experimental configuration allows one to observe, however, the input and the output pulse profiles only. We report an original nondestructive technique for observation of a spatial propagation of the pulses via observation of the transient fluorescence excited by the propagating light-pulses at the fiber side, from which we are able to reconstruct how does the fractional delay and the amplitude of the propagating pulses change along the fiber. Results of a numerical simulation of the nonlinear pulse propagation performed for a saturable two-level medium in low contrast approximation proved to be in a reasonable agreement with the experimental observations.